Abstract
We present FUSE observations of O VI lambda lambda 1032, 1038 emission from non-radiative and radiative shocks in the Cygnus Loop supernova remnant. The velocity profiles of the lines and the spatial variation of their fluxes can be used to study the distribution of the emitting components and the shock geometry. The ratio between the fluxes of the two components can be used to evaluate the effects of both resonance scattering and absorption by material along the line of sight. The O VI emission varies systematically with the H alpha behind smooth non-radiative shocks but the two are distributed very differently in complex shock-cloud interactions. O VI traces gas at about 300,000 K, hotter than the optical filaments and cooler than the X-ray regions, and thus provides a crucial diagnostic for multi-wavelength studies of SNR shocks.
